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| author | Simon Marlow <marlowsd@gmail.com> | 2011-10-07 14:47:51 +0100 |
|---|---|---|
| committer | Simon Marlow <marlowsd@gmail.com> | 2011-10-10 10:45:47 +0100 |
| commit | f65bbbe02555b20e219e4ad3a540d385ae393092 (patch) | |
| tree | df804b829c5efc2907a7eacdc5e2c523045ef454 /docs | |
| parent | fa278b82730c2d18297bc9c8567b1b35a8769f5f (diff) | |
| download | haskell-f65bbbe02555b20e219e4ad3a540d385ae393092.tar.gz | |
document the -H option
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/runtime_control.xml | 38 |
1 files changed, 23 insertions, 15 deletions
diff --git a/docs/users_guide/runtime_control.xml b/docs/users_guide/runtime_control.xml index 48ea0a875b..2af87bcc41 100644 --- a/docs/users_guide/runtime_control.xml +++ b/docs/users_guide/runtime_control.xml @@ -543,26 +543,34 @@ char *ghc_rts_opts = "-H128m -K1m"; <varlistentry> <term> - <option>-H</option><replaceable>size</replaceable> + <option>-H</option><optional><replaceable>size</replaceable></optional> <indexterm><primary><option>-H</option></primary><secondary>RTS option</secondary></indexterm> <indexterm><primary>heap size, suggested</primary></indexterm> </term> <listitem> <para>[Default: 0] This option provides a - “suggested heap size” for the garbage collector. The - garbage collector will use about this much memory until the - program residency grows and the heap size needs to be - expanded to retain reasonable performance.</para> - - <para>By default, the heap will start small, and grow and - shrink as necessary. This can be bad for performance, so if - you have plenty of memory it's worthwhile supplying a big - <option>-H</option><replaceable>size</replaceable>. For - improving GC performance, using - <option>-H</option><replaceable>size</replaceable> is - usually a better bet than - <option>-A</option><replaceable>size</replaceable>.</para> - </listitem> + “suggested heap size” for the garbage + collector. Think + of <option>-H<replaceable>size</replaceable></option> as a + variable <option>-A</option> option. It says: I want to + use at least <replaceable>size</replaceable> bytes, so use + whatever is left over to increase the <option>-A</option> + value.</para> + + <para>This option does not put + a <emphasis>limit</emphasis> on the heap size: the heap + may grow beyond the given size as usual.</para> + + <para>If <replaceable>size</replaceable> is omitted, then + the garbage collector will take the size of the heap at + the previous GC as the <replaceable>size</replaceable>. + This has the effect of allowing for a + larger <option>-A</option> value but without increasing + the overall memory requirements of the program. It can be + useful when the default small <option>-A</option> value is + suboptimal, as it can be in programs that create large + amounts of long-lived data.</para> + </listitem> </varlistentry> <varlistentry> |